Change GetNodeDaemonPort to GetDaemonPort in utils

GetNodeDaemonPort is used to lookup the node daemon port in the services
file, and if not found to return the default one. We make it a generic
function, which accepts the daemon name in input, so that it can be used
by confd as well, to lookup its own udp port.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>